Hello there,
A more scale-friendly alternative to the previous answers, using SVG:
' CallBehaviorAction (activity vs. action)
' (adapted from https://github.com/plantuml/plantuml/discussions/1066)
' SVG adapted from https://www.svgrepo.com/svg/412621/harvest
' (https://www.svgrepo.com/show/412621/harvest.svg)
sprite calBehaviorAction <svg viewBox="0 0 32 32" xml:space="preserve">
<path d="M26,14v14h-4V18h-4v10h-4V18h-4v10H6V14h8V4h4v10H26z"/>
</svg>
' Example of use
':Activity name\n <$calBehaviorAction{scale=0.5}>;
' Put as much space as needed so that the the symbol becomes correctly aligned.
start
:This is an action;
:The next element
is an activity;
:An activity can be seen
as an abstraction level
of a set of actions <$calBehaviorAction{scale=0.5}>;
:Hope that helps!;
stop
@enduml